A belief that human intelligence could guide evolution led the world to concentration camps

At a time when science promises such dazzling advances in the practice of medicine, it may be prudent to cast a glance over the shoulder, back to an earlier era when scientists--or people who thought they were doing science--stirred hopes that better days were only a generation or so away. The rise and fall of the theory known as eugenics is in every respect a cautionary tale. The early eugenicists were usually well-meaning and progressive types. They had imbibed their Darwin and decided that the process of natural selection would improve if it were guided by human intelligence. They did not...